chr18-2694694-G-A

Variant names:

Variant summary

Our verdict is Pathogenic. The variant received 12 ACMG points: 16P and 4B. PVS1PP5_Very_StrongBS2

The NM_015295.3(SMCHD1):c.1040+1G>A variant causes a splice donor, intron change involving the alteration of a conserved nucleotide. The variant allele was found at a frequency of 0.00000373 in 1,609,140 control chromosomes in the GnomAD database, with no homozygous occurrence. In-silico tool predicts a pathogenic outcome for this variant. 3/3 splice prediction tools predicting alterations to normal splicing. Variant has been reported in ClinVar as Pathogenic (★★).

Frequency

Genomes: 𝑓 0.0000066 ( 0 hom., cov: 32)

Exomes 𝑓: 0.0000034 ( 0 hom. )

Consequence

SMCHD1
NM_015295.3 splice_donor, intron

Scores

Splicing: ADA: 1.000

Clinical Significance

Pathogenic criteria provided, multiple submitters, no conflicts P:2

Conservation

PhyloP100: 8.90

Publications

2 publications found

Variant links:

Genes affected

SMCHD1 (HGNC:29090): (structural maintenance of chromosomes flexible hinge domain containing 1) This gene encodes a protein which contains a hinge region domain found in members of the SMC (structural maintenance of chromosomes) protein family. [provided by RefSeq, Dec 2011]

SMCHD1 Gene-Disease associations (from GenCC):

arhinia, choanal atresia, and microphthalmia
Inheritance: AD Classification: DEFINITIVE, STRONG Submitted by: Labcorp Genetics (formerly Invitae), PanelApp Australia, G2P, Ambry Genetics, ClinGen, Illumina
facioscapulohumeral muscular dystrophy
Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet
hyposmia-nasal and ocular hypoplasia-hypogonadotropic hypogonadism syndrome
Inheritance: AD Classification: SUPPORTIVE Submitted by: Orphanet

SMCHD1 links:

ENSG00000266049 (HGNC:):

ENSG00000266049 links:

Genome browser will be placed here

ACMG classification

Classification was made for transcript

Our verdict: Pathogenic. The variant received 12 ACMG points.

PVS1

Splicing +-2 bp (donor or acceptor) variant, LoF is a know mechanism of disease, No cryptic splice site detected. Exon removal results in frameshift change.

PP5

Variant 18-2694694-G-A is Pathogenic according to our data. Variant chr18-2694694-G-A is described in ClinVar as [Pathogenic]. Clinvar id is 464158.Status of the report is criteria_provided_multiple_submitters_no_conflicts, 2 stars.

BS2

High AC in GnomAdExome4 at 5 AD gene.

Transcripts

RefSeq

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	MANE	Protein	UniProt
SMCHD1	NM_015295.3 link	c.1040+1G>A		splice_donor_variant, intron_variant	Intron 8 of 47	ENST00000320876.11	NP_056110.2

Ensembl

Gene	Transcript	HGVSc	HGVSp	Effect	Exon rank	TSL	MANE	Protein	Appris	UniProt
SMCHD1	ENST00000320876.11 link	c.1040+1G>A		splice_donor_variant, intron_variant	Intron 8 of 47	5	NM_015295.3	ENSP00000326603.7		A6NHR9-1

Frequencies

GnomAD3 genomes

AF:

0.00000657

AC:

AN:

152136

Hom.:

Cov.:

show subpopulations

Gnomad AFR

AF:

0.00

Gnomad AMI

AF:

0.00

Gnomad AMR

AF:

0.00

Gnomad ASJ

AF:

0.00

Gnomad EAS

AF:

0.00

Gnomad SAS

AF:

0.00

Gnomad FIN

AF:

0.00

Gnomad MID

AF:

0.00

Gnomad NFE

AF:

0.0000147

Gnomad OTH

AF:

0.00

GnomAD4 exome

AF:

0.00000343

AC:

AN:

1457004

Hom.:

Cov.:

AF XY:

0.00000414

AC XY:

AN XY:

724856

show subpopulations

African (AFR)

AF:

0.00

AC:

AN:

33144

American (AMR)

AF:

0.00

AC:

AN:

43242

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

25988

East Asian (EAS)

AF:

0.00

AC:

AN:

39606

South Asian (SAS)

AF:

0.00

AC:

AN:

85378

European-Finnish (FIN)

AF:

0.0000187

AC:

AN:

53376

Middle Eastern (MID)

AF:

0.00

AC:

AN:

5724

European-Non Finnish (NFE)

AF:

0.00000360

AC:

AN:

1110348

Other (OTH)

AF:

0.00

AC:

AN:

60198

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.405

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Age Distribution

Exome Het

Variant carriers

<30

30-35

35-40

40-45

45-50

50-55

55-60

60-65

65-70

70-75

75-80

>80

Age

GnomAD4 genome

AF:

0.00000657

AC:

AN:

152136

Hom.:

Cov.:

AF XY:

0.00

AC XY:

AN XY:

74316

show subpopulations

⚠️ The allele balance in gnomAD version 4 Genomes is significantly skewed from the expected value of 0.5.

African (AFR)

AF:

0.00

AC:

AN:

41418

American (AMR)

AF:

0.00

AC:

AN:

15274

Ashkenazi Jewish (ASJ)

AF:

0.00

AC:

AN:

3472

East Asian (EAS)

AF:

0.00

AC:

AN:

5196

South Asian (SAS)

AF:

0.00

AC:

AN:

4834

European-Finnish (FIN)

AF:

0.00

AC:

AN:

10604

Middle Eastern (MID)

AF:

0.00

AC:

AN:

316

European-Non Finnish (NFE)

AF:

0.0000147

AC:

AN:

68018

Other (OTH)

AF:

0.00

AC:

AN:

2094

⚠️ The allele balance in gnomAD version 4 Genomes is significantly skewed from the expected value of 0.5. (p-value = 0.000000), which strongly suggests a high chance of mosaicism in these individuals.

Allele Balance Distribution

Red line indicates average allele balance

Average allele balance: 0.375

Heterozygous variant carriers

0.00

0.20

0.40

0.60

0.80

0.95

Allele balance

Alfa

AF:

0.00

Hom.:

Bravo

AF:

0.00000378

ClinVar

Significance: Pathogenic

Submissions summary: Pathogenic:2

Revision: criteria provided, multiple submitters, no conflicts

LINK: link

Submissions by phenotype

Facioscapulohumeral muscular dystrophy 2

Pathogenic:1

Jan 06, 2025

Labcorp Genetics (formerly Invitae), Labcorp

Significance:Pathogenic

Review Status:criteria provided, single submitter

Collection Method:clinical testing

This sequence change affects a donor splice site in intron 8 of the SMCHD1 gene. It is expected to disrupt RNA splicing. Variants that disrupt the donor or acceptor splice site typically lead to a loss of protein function (PMID: 16199547), and loss-of-function variants in SMCHD1 are known to be pathogenic (PMID: 23143600). This variant is not present in population databases (gnomAD no frequency). Disruption of this splice site has been observed in individual(s) with facioscapulohumeral-like muscular dystrophy (PMID: 24755953). It has also been observed to segregate with disease in related individuals. ClinVar contains an entry for this variant (Variation ID: 464158). Algorithms developed to predict the effect of sequence changes on RNA splicing suggest that this variant may disrupt the consensus splice site. For these reasons, this variant has been classified as Pathogenic. -

not provided

Pathogenic:1

Sep 28, 2022

GeneDx

Significance:Pathogenic

Review Status:criteria provided, single submitter

Collection Method:clinical testing

Not observed at significant frequency in large population cohorts (gnomAD); Canonical splice site variant predicted to result in a null allele in a gene for which loss of function is a known mechanism of disease (Winston et al. 2015); This variant is associated with the following publications: (PMID: 24755953, Hiramuki2022[Preprint]) -

Computational scores

Source: dbNSFP v4.3

Name

Calibrated prediction

Score

Prediction

BayesDel_addAF

Pathogenic

0.63

BayesDel_noAF

Pathogenic

0.40

CADD

Pathogenic

(source)

DANN

Uncertain

1.0

Eigen

Pathogenic

1.2

Eigen_PC

Pathogenic

1.1

FATHMM_MKL

Pathogenic

0.99

PhyloP100

8.9

GERP RS

5.3

RBP_binding_hub_radar

0.0

RBP_regulation_power_radar

1.7

Mutation Taster

=0/100

disease causing (ClinVar)

(source)

Splicing

Name

Calibrated prediction

Score

Prediction

dbscSNV1_ADA

Pathogenic

1.0

dbscSNV1_RF

Pathogenic

0.94

SpliceAI score (max)

1.0

Details are displayed if max score is > 0.2

DS_DG_spliceai

0.42

Position offset: 3

DS_DL_spliceai

1.0

Position offset: -1

Find out detailed SpliceAI scores and Pangolin per-transcript scores at spliceailookup.broadinstitute.org

Publications

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Variant summary

Frequency

Consequence

Scores

Clinical Significance

Conservation

Publications

ACMG classification

Transcripts

RefSeq

Ensembl

Frequencies

Age Distribution

ClinVar

Submissions by phenotype

Computational scores

Splicing

Publications

Other links and lift over